Mapping nanoscale topographic features in thick tissues with speckle diffraction tomography

Resolving three-dimensional morphological features in thick specimens remains a significant challenge for label-free imaging. We report a new speckle diffraction tomography (SDT) approach that can image thick biological specimens with ~500 nm lateral resolution and ~1 μm axial resolution in a reflection geometry. In SDT, multiple-scattering background is rejected through spatiotemporal gating provided by dynamic speckle-field interferometry, while depth-resolved refractive index maps are reconstructed by developing a comprehensive inverse-scattering model that also considers specimen-induced aberrations. Benefiting from the high-resolution and full-field quantitative imaging capabilities of SDT, we successfully imaged red blood cells and quantified their membrane fluctuations behind a turbid medium with a thickness of 2.8 scattering mean-free paths. Most importantly, we performed volumetric imaging of cornea inside an ex vivo rat eye and quantified its optical properties, including the mapping of nanoscale topographic features of Dua's and Descemet's membranes that had not been previously visualized.

MicroRNA-19a-PTEN Axis Is Involved in the Developmental Decline of Axon Regenerative Capacity in Retinal Ganglion Cells

Irreversible blindness from glaucoma and optic neuropathies is attributed to retinal ganglion cells (RGCs) losing the ability to regenerate axons. While several transcription factors and proteins have demonstrated enhancement of axon regeneration after optic nerve injury, mechanisms contributing to the age-related decline in axon regenerative capacity remain elusive. In this study, we show that microRNAs are differentially expressed during RGC development and identify microRNA-19a (miR-19a) as a heterochronic marker; developmental decline of miR-19a relieves suppression of phosphatase and tensin homolog (PTEN), a key regulator of axon regeneration, and serves as a temporal indicator of decreasing axon regenerative capacity. Intravitreal injection of miR-19a promotes axon regeneration after optic nerve crush in adult mice, and it increases axon extension in RGCs isolated from aged human donors. This study uncovers a previously unrecognized involvement of the miR-19a-PTEN axis in RGC axon regeneration, and it demonstrates therapeutic potential of microRNA-mediated restoration of axon regenerative capacity in optic neuropathies.

Impact of PTEN/SOCS3 deletion on amelioration of dendritic shrinkage of retinal ganglion cells after optic nerve injury

Retinal ganglion cell (RGC) degeneration, leading to irreversible blindness in chronic optic neuropathies, commonly begins with dendritic shrinkage followed by axon degeneration. Although limited axon regeneration in the optic nerve is possible with a genetic deletion of PTEN/SOCS3 after optic nerve injury, the roles of PTEN/SOCS3 on dendritic preservation and regeneration remain unclear. This study investigated the effect of PTEN/SOCS3 genetic deletion on the structural integrity of RGC dendrites and axons in the retina following optic nerve crush. Using time-lapse, in vivo confocal scanning laser ophthalmoscopy to serially image dendritic and axonal arborizations of RGCs over six months after injury, RGC dendrites and axons were only preserved in Thy-1-YFP/PTEN^-/- and Thy-1-YFP/PTEN^-/-SOCS3^-/- mice, and axons in the retina regenerated at a rate of 21.1 μm/day and 15.5 μm/day, respectively. By contrast, dendritic complexity significantly decreased in Thy-1-YFP-SOCS3^-/- and control mice at a rate of 7.0 %/day and 7.1 %/day, respectively, and no axon regeneration in the retina was observed. RGC survival probability was higher in Thy-1-YFP/PTEN^-/- and Thy-1-YFP/PTEN^-/-SOCS3^-/- mice compared with Thy-1-YFP-SOCS3^-/- and control mice. The differential responses between the transgenic mice demonstrate that although a genetic deletion of PTEN, SOCS3, or PTEN/SOCS3 allows partial axon regeneration in the optic nerve after optic nerve crush, a deletion of PTEN, but not SOCS3, ameliorates RGC dendritic shrinkage. This shows that the signaling pathways involved in promoting axon regeneration do not equally contribute to the preservation of dendrites, which is crucial to the translational application of neuroregenerative therapies for visual restoration.

Intracameral injection of a chemically cross-linked hydrogel to study chronic neurodegeneration in glaucoma

Investigation of neurodegeneration in glaucoma, a leading cause of irreversible blindness worldwide, has been obfuscated by the lack of an efficient model that provides chronic, mild to moderate elevation of intraocular pressure (IOP) with preservation of optical media clarity for long term, in vivo interrogation of the structural and functional integrity of the retinal ganglion cells (RGCs). Here, we designed and formulated an injectable hydrogel based on in situ cross-linking of hyaluronic acid functionalized with vinyl sulfone (HA-VS) and thiol groups (HA-SH). Intracameral injection of HA-VS and HA-SH in C57BL/6J mice exhibited mild to moderate elevation of IOP with daily mean IOP ranged between 14 ± 3 and 24 ± 3 mmHg, which led to progressive, regional loss of RGCs evaluated with in vivo, time-lapse confocal scanning laser ophthalmoscopy; a reduction in fractional anisotropy in the optic nerve and the optic tract projected from the eye with increased IOP in diffusion tensor magnetic resonance imaging; a decrease in positive scotopic threshold response in electroretinography; and a decline in visual acuity measured with an optokinetic virtual reality system. The proportion of RGC loss was positively associated with the age of the animals, and the levels and the duration of IOP elevation. The new glaucoma model recapitulates key characteristics of human glaucoma which is pertinent to the development and pre-clinical testing of neuroprotective and neuroregenerative therapies. STATEMENT OF SIGNIFICANCE: A new model to study chronic neurodegeneration in glaucoma has been developed via intracameral injection of a specifically designed hyaluronic acid functionalized with vinyl sulfone and thiol groups for cross-linking. Intracameral injection of the chemically cross-linked hydrogel generates mild to moderate IOP elevation, resulting in progressive degeneration of the retinal ganglion cells, optic nerve, and optic tract, and a decline in visual function. The model recapitulates the key features of neurodegeneration in human glaucoma, which will facilitate and expedite the development of neuroprotective and neuroregenerative therapies.

Evaluation of carotid stenosis using CT angiography in the initial evaluation of stroke and TIA

BACKGROUND

Imaging of the carotid arteries is important for the evaluation of patients with ischemic stroke or TIA. CT angiography (CTA) of the head and neck is readily available and can be part of the routine imaging of stroke patients. To evaluate the accuracy of CTA, the authors compared the degree of stenosis found using CTA with digital subtraction angiography (DSA) in consecutive patients during a 3-year period.

METHODS

The authors included all patients with interpretable CTA and DSA of the cervical carotid arteries from April 2000 to November 2002 at a single academic medical center. This yielded a total of 81 vessels. Stenosis on CTA of the internal carotid artery was measured in the axial plane at the point of maximum stenosis and referenced to the distal cervical internal carotid by two blinded readers. Two blinded readers measured stenosis from the DSA using the North American Symptomatic Carotid Endarterectomy Trial method.

RESULTS

Using a 70% cutoff value for stenosis, CTA and DSA were in agreement in 78 of 81 (96%; 95% CI, 90 to 99%) vessels. CTA was 100% sensitive (n = 5) and 63% specific (95% CI, 25 to 88%), and the negative predictive value of a CTA demonstrating <70% stenosis was 100% (n = 73).

CONCLUSIONS

In this consecutive series of patients with CT angiography of the neck and digital subtraction angiography, the authors found that CT angiography has a high sensitivity and high negative predictive value for carotid disease. CT angiography appears to be an excellent screening test for internal carotid artery stenosis, and the authors advocate its use for the initial imaging of patients with suspected stroke or TIA.

Dural metastasis at medulla oblongata: a rare cause of vocal fold paralysis

Malignancy is a major cause of vocal fold paralysis. Nevertheless, metastatic disease at the brainstem leading to high vagal paralysis is rarely encountered. We illustrate an unusual case of unilateral vocal fold paralysis caused by dural metastasis directly compressing on the nucleus ambiguus. The median position of the paralysed vocal fold is inconsistent with the Wagner and Grossman theory predicting the location of the lesion.

Radiation exposure reduction by use of Kevlar cassettes in the neonatal nursery

A study was performed to determine whether the use of Kevlar cassettes in the neonatal intensive care nursery would reduce radiation exposure to patients. The radiation dose to the neonates was measured by using thermoluminescent dosimeters. In addition, the attenuation of the Kevlar cassettes and the sensitivity of the film-screen combination were compared with the previously used system. The greatest radiation reduction using a mobile X-ray unit was 27%; based on sensitivity measurements, the theoretical reduction averaged 38%. The reduction in radiation exposure resulted from reduced attenuation by the Kevlar cassette.

Hospital outpatient medical summary

The rationale for having a hospital outpatient summary is discussed. A design is proposed which is complementary to a priorly proposed inpatient-episode summary aiming at speedy information retrieval while providing for efficient referencing. It has the following features: It records chronologically the essentials of the evolving health status and its management in the outpatient mode. It is especially formatted to accommodate the multispecialty orientation in the outpatient setting. It registers the evolution of previous diagnoses and health problems to give a clear background picture of prior health status. There is flexibility to allow for editing and arbitrary cut-offs for special situations. It is simple and easy to implement. It is computer compatible.

A chronologically-organized ongoing data entry holistic-approach hospital inpatient-episode summary

A comprehensive hospital inpatient summary is designed to cater for all the identified needs of professional users. The hallmark characteristic of the design is its basic concept towards resolving the dilemma of registering only the essence while possessing capabilities for efficacious access to full details. It is easily comprehensible and has a holistic integral approach with the following features: A summary of the evolving diagnoses and health problems of the current episode of hospitalisation; it also records general health status, salient features of management for each condition, and an appended list of past diagnoses and health problems. Information about the mode of admission and separation are recorded, with special provision for continuing after care. Data are dated entered on an ongoing basis. While keeping input to the bare essence it functions also as a lynch-pin for effective speedy access to full details through the referencing propensities of dated-data. Provisions are made for tracking previous records. It allows for editing, and so is flexible and expandable. Combined techniques, including tabulations and simple symbol systems, are utilised for ultimate brevity. It is compatible with existing record systems. It is computer compatible.